Author Topic: The Devil in my engine.  (Read 2860 times)

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Offline george sutton

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The Devil in my engine.
« on: 14 Jul 2013 at 15:15 »
As many of you may recall from old posts, i acquired my 1947 engined ,48 bike four years ago.Looking beautiful, basically it was a lot of crap and bad parts put together to make the perfect crap m/c.  Bores so badly pitted they could'nt be oversized, and had been fitted with 0.040"rings that did not help. Also fitted with a mixture of mk.1 & mk.5 valve springs.  Good old Brian Thorby got me off to a good start by donateing a couple of barrels ( one, an 8 finner!, remember Brian?)..rebored then 0.020", with new pistons,,valves, guides,and springs. carbs were carefully set up on the bench to give equal operation. made new float bowl tops in brass,fitted new jets an needles. BUT,STILL, it would not run properly on both cylinders.   knowing that the magneto also had problems, I got Dave Lindsley to rebuild it. Rewound, end plate realigned, new camring fitted, it now runs strong and regular under compression. BUT still it would'nt run correctly on both cylinders, or restart when warm! Finding a compression loss on cylinders, revealed piston rings had gapped out to 0.025". (running in on the stand)..   new rings fitted gapping at 0.006"but still no joy! only left now with a relook at the carbs. Remembering what Eric morley told me about useing 4/4 cutaway slides, i contacted AMAL carbs. they could no longer supply them. they put me on Autocycle engineering. A chance conversation with a gent who really knew the 274 carbs, revealed i'd got overbored carb bodies to 0.021",fitted with undersized throttle valves. NO WONDER, i was having problems. But they no longer made valves nor could supply the brass tubeing for it.Up the creek again, i was'nt giving up.   I bought 30 m/m dia.solid brass,and last week i made a pair of 3 1/2 cutaway valves myself.  Now fitted,they work well,run on BOTH cyl. and ,restart from warm! Great thought i , MALDON meet here i come.  Oyea!! now suddenly, for the first time when i switch off, oil drips Very fast from the bottom of the flywheel bell housing  HOW can this be ? It was only march this year i put the whole unit back in , having rebuilt the noisey gearbox with a new primery imput shaft and seal !  IS there a Douglas owning vicar out there who can come an do an exorcism on this damb m/c???  I said i'd never been beaten by an engine in over 60 years and i would not give up . But guys i truely am weakening!

Offline eddie

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Re: The Devil in my engine.
« Reply #1 on: 14 Jul 2013 at 17:19 »
George,
            First of all, make sure that neither the engine or gearbox is overfilled with oil. Check that the gearbox filler has a breather hole (they are identical to the engine filler except for the breather hole). If there is no hole, then the oil is probably being pushed back up the drain hole to the input shaft and leaking from the bellhousing.
     The oil could also be coming from the engine. Make sure there are no leaks around the clutch spigot or the crankshaft oilseal. The oilseal should have been oiled prior to fitting as a dry seal will cut into the shaft resulting in a premature leak. Another place oil can leak from is the plugs at the back of the camshafts - it is not unheard of for these plugs to drop out if not correctly fitted - Mr Douglas supplied them in various oversizes to try to overcome this problem.
  Regards,
               Eddie.

Offline george sutton

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Re: The Devil in my engine.
« Reply #2 on: 14 Jul 2013 at 18:41 »
Hi Eddie, many thanks for your feedback.   My first thought as it had'nt before, was of course the oil level and breather hole.  with the engine on the bench, sep. from the g/box ,there was no sign of oil in the housing either. Only last week i had the timing cover off to finally check the mag .and points, no sign of trouble.   As to the rest, i dont want to think about pulling it out again.   As an example. In april i worked so hard to beat this genie, that at 2am on my 80th birthday i began a  severe nose bleed, that took a hosp. ENT unit 4 days to stop.  Thanks Eddie.

Offline george sutton

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Re: The Devil in my engine.
« Reply #3 on: 15 Jul 2013 at 09:48 »
Eddie,   That timing cover i said i took off last week !  remembered last night, that i'd partly drained some oil out, then, put it back filtered, plus a small amount to cover the  loss.  a quick check this morn, showed i had gone just over the high mark.  Have drained off 1/2 pint, run up till good and hot, and zippo, i've got a dry bottom, in both sences of the word!  That is of course on the bike stand, what will happen when off, and the engine is slightly angled down, i 've yet to see. Denis.